6io 



NA TURE 



[October 20, 1904 



solutions which contain three hundred times as much 

 mag-nesium oxalate as that present in the saturated solution 

 of the hydrated salt. Electrical measurements show that 

 the equivalent conductivity decreases at an abnormally high 

 rate as the concentration increases. This and other pheno- 

 mena furnish strong evidence in support of the view that 

 polymerised molecules are present in the solution in con- 

 siderable proportion. 



A SECOND edition of Mr. Borchardt's " Arithmetical 

 Examples," to which twenty-four pages of new exercises, 

 oral and otherwise, have been added, has been published by 

 Messrs. Rivingtons. 



A " Geometrical Political Economy," by Mr. H. Cunyng- 

 hame, C.B., is about to be published by the Oxford Uni- 

 versity Press. The work is an elementary treatise on the 

 method of explaining some of the theories of pure economic 

 science by means of diagrams. 



The October issue of the Popular Science Monthly is 

 devoted entirely to the Cambridge meeting of the British 

 Association. Dr. Pritchett, president of the Massachusetts 

 Institute of Technology, contributes " A Traveller's View 

 of the British Association Meeting," and in addition are 

 included the presidential addresses of the Prime Minister, 

 Prof. Horace Lamb, Mr. W. Bateson, Mr. Francis Darwin, 

 Mr. Henry Balfour, Mr. Douglas Freshfield, Prof. C. S. 

 Sherrington, and the Hon. Charles A. Parsons. 



OUR ASTRONOMICAL COLUMN. 



Encke's Comet. — ^The absence of further observations of 

 Encke's comet has caused some doubt to be e.xpressed as to 

 the correctness of Herr Kopff's conclusion regarding the 

 identity of the object which he obtained on his photograph 

 of September ii. 



In the Astronomische Nachrichten, No. 3970, the same 

 observer states that he has obtained confirmatory evidence 

 which places the identity beyond doubt, although'the comet 

 is still extremely faint and diffuse. On a photograph ex- 

 posed on September 17, at I3h. 2q.2m. (Heidelberg M.T.), 

 the same object appeared in the following position : — 



R.A. = ih. 40-6m^ dec. = -1-26° 14'. 



On comparing this position, and the one determined in 

 the first observation (September 11), with the interpolated 

 values obtained from the ephemeris published by MM. 

 Ocoulitsch and Kaminsky, it is seen that the ephemeris 

 requires the following approximate corrections : — 



— 0.7m. and — 6'o. 



Herr P. Gotz, of Heidelberg, was unable to find the 

 comet on September 6 with a 6-inch telescope. 



Structure of the Oxygen Bands in the Solar Spectrum. 

 — In the September number of the Aslrophysical Journal 

 Mr. O. C. Lester, of the Sloane Physical Laboratory, Yale 

 University, discusses the results recently obtained bv him 

 in a research as to the nature of the o.xygen bands in the 

 solar spectrum, of which the B group is a tvpical example. 



The purpose of the research was to investigate the 

 relations existing between the lines of each band and between 

 the several bands, including in the latter two bands above 

 a which do not appear to have been discussed previously. 



The results may be summarised as follows : — (i) More 

 accurate measures of the wave-lengths of the lines in groups 

 A, B, and a have been made, the a' band has been measured 

 for the first time, and a new group (a") at A 5377-2 has 

 been discovered and its lines measured. (2) It has been 

 shown that the oxygen absorption spectrum consists of two 

 distinct series of bands, instead of one, which occur in pairs 

 similarly to the series of lines in a band. (3) Deslandre's 

 first law concerning the distribution of lines in a spectral 



NO. 1825, VOL. 70] 



band, viz. '^ = a + bn- (where N = the vibration frequency 

 number, a and b are constants, and n takes on all integral 

 values from o to n), is shown to be inadequate to represent 

 the line series of the several bands. A modification of this 

 formula suggested by Mr. Lester is 



N = a-f fen-fc-'n^, 



and this represents the series within the limits of observ- 

 ational errors : c and k are constants which are different for 

 each series, although the differences are but small. 



Recurrent Markings on Jupiter. — From the inspection 

 of several thousand drawings of Jupiter made during the 

 last half-century, Mr. Denning has arrived at the conclusion 

 that " features exhibiting various peculiarities of appear- 

 ance and rates of motion are common to certain latitudes 

 and break out from time to time, enduring for certain un- 

 known intervals, then disappearing to be replaced by similar 

 phenomena." Some exceptional outbreaks, no doubt, only 

 take place at long intervals, whilst the evidences of others 

 remain visible for long periods. 



Mr. Denning suggests that if the old drawings could be 

 collected and suitably discussed, considerable light might 

 be thrown on the physical changes which are ever taking 

 place. The value of this discussion must, in a measure, 

 depend upon the continuitv of the observations, and it is 

 suggested that, as Jupiter is now being continuously 

 observed and delineated, there will in a few years be ample 

 material for such a discussion. 



In the meantime Mr. Denning suggests that further in- 

 sight into the wonderful atmospheric phenomena of the 

 planet might be obtained from a study of the large number 

 of drawings made by Schwabe between 1830 and i860, and 

 the 300 or 400, or more, made by Schmidt between 1843 and 

 1880 (the Observatory, October, 1904). 



Comparison of the Intensities of Photographic 

 Stellar Images. — The second chapter of the " Instructions 

 to Variable .Star Observers," of which the first chapter was 

 summarised in these columns on September 15, is published 

 in the October number of the Bulletin de la Societt' astro- 

 nomique de France. Variable star observers will find many 

 points of interest and instruction in the present chapter, 

 which deals with the details of obtaining suitable photo- 

 graphs, and afterwards comparing and reducing the plates. 



Observations in the Southern Hemisphere. — The Lick 

 Observatory expedition to the southern hemisphere installed 

 its apparatus at Santiago de Chile during the southern 

 winter of 1903, and commenced observations on September 11 

 ('903)- 



A detailed description of the instruments in use, the 

 observations and results, is promised for a later publication, 

 but in the meantime Prof. W. H. Wright records several 

 important results obtained with a powerful three-prism 

 spectroscope attached to a Cassegrainian reflector of 

 04 cm. aperture, in No. 2, vol. .xx., of the .istrophysical 

 Journal, 



The stars /3 Doradus, to \'plorum, / Carinae, k Pavonis, 

 and T Sagittarii, have been found to have variable radial 

 velocities. 



Observations of a Centauri have also been made, and 

 indicate an average difference between the radial velocities 

 of the two components of about 5.17 km. One probable 

 explanation as to the cause of this difference is that it is 

 due to the relative orbital motion of the two components, 

 and if this is true the parallax of the system may be deter- 

 mined, because the visual orbit of the pair is already well 

 known. Dr. Palmer made the computation, and obtained 

 the following results : — 



IT = 076" 



a = 3'46 ■: 10^ km. 

 mi + m„= 19. 



a = mean distance between components in kilometres, m, and 

 111, = the respective masses of a, and a, Centauri in terms 

 of the sun's mass. 



The relative masses of the components, as previously 

 determined, is about 51 : 49 in favour of the brighter. The 

 spectrum of the latter is of the solar type, whilst in that of 

 the fainter the iron lines are more pronounced and the 

 calcium absorption is exceedingly heavy. 



